Research Design: It is hypothesized that 24 Veterans with chronic PTSD who are randomly assigned to adopt a dog from the San Antonio Humane Society shortly after randomization (the experimental group) will - after adjusting for baseline scores -- have a mean score on the PTSD Checklist - Stressor Specific Version (PCL-S) 3 months post-randomization that is significantly lower than the 24 Veterans who do not adopt a dog until after a 3-month waiting period (the control group). It is also hypothesized that the difference in means between the two groups will be at least 10 points, a clinically meaningful amount. In addition, it is hypothesized that the clinical improvement in the experimental group will be maintained at 6 months and that the control subjects will show a clinically meaningful improvement in their PCL-S scores 3 months after they adopt a dog. As part of the study's secondary aims, changes in Veterans' other psychological symptoms, health-related quality of life, community integration, and physical health and health-related behaviors will also be assessed. Methods: To enroll in the study, male and female Veterans will need to be at least 18 years of age and to have served during the Vietnam era or more recently. Inclusion criteria will include a current DSM-IV-TR diagnosis of PTSD, as determined by the PTSD Symptom Scale Interview (PSS-I), a score of >50 on the PCL-S, and a history of having had a dog previously, but not in the past year. Exclusion criteria will include current substance abuse or dependence; psychosis, mania, psychiatric hospitalization, or significant suicidal ideation within the past 3 months; and a history of moderate or severe traumatic brain injury. Veterans will be assisted in choosing a dog that is closely suited to them in terms of age, breed, size, and temperament. Dogs will receive vaccinations, 6 months of heartworm and flea medication, be spayed or neutered, and have a microchip implanted under their skin to facilitate finding them if they get lost. Animals with a known chronic medical condition will not be adopted. Veterans will be given a certificate for a free check-up for their pet at a collaborating veterinary clinic within 2 weeks of adoption. The Humane Society will also instruct veterans in how to care for their dog, offer free obedience classes, and provide free advice at any time for any questions or problems. All Veterans will have follow-up visits 1, 3, and 6 months following randomization, with the control group having an additional visit at 4 months. All participants will also receive frequent phone calls from study staff to monitor their progress.